300-510 · Question #102
Refer to the exhibit. All routers on this network have been configured with PIM-SM, and R1 is the rendezvous point. However, when asymmetric routing is implemented to modify link usage, the network…
The correct answer is C. Add a static Mroute for routes that are failing. PIM-SM relies on RPF (Reverse Path Forwarding) checks to validate that multicast traffic arrives on the correct interface-the one closest to the source according to the unicast routing table. With asymmetric routing, the path packets take through the network differs depending…
Question
Refer to the exhibit. All routers on this network have been configured with PIM-SM, and R1 is the rendezvous point. However, when asymmetric routing is implemented to modify link usage, the network begins to drop certain multicast traffic. Which action corrects the problem?
Options
- APlace the routes affected by asymmetric routing in a VRF.
- BRemove the asymmetric routing and use spanning tree to manage link usage.
- CAdd a static Mroute for routes that are failing.
- DConfigure the routers to use PIM-DM instead of PIM-SM.
How the community answered
(33 responses)- A6% (2)
- B12% (4)
- C79% (26)
- D3% (1)
Explanation
PIM-SM relies on RPF (Reverse Path Forwarding) checks to validate that multicast traffic arrives on the correct interface-the one closest to the source according to the unicast routing table. With asymmetric routing, the path packets take through the network differs depending on direction, so multicast traffic may arrive on an interface that fails the RPF check, causing the traffic to be dropped. A static Mroute (ip mroute) overrides the RPF lookup for specific sources or groups, pointing PIM to the correct upstream interface even when the unicast table would select a different one. This directly solves the RPF failure caused by asymmetric routing without removing the asymmetric policy.
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